In a large number of processes such as for instance coal gasification, refuse burning and processes in the chemical or metal industries, large quantities of waste are released. This waste contains different sorts of contaminants, such as organic matter in the form of petroleum and oil for example and heavy metals.
The treatment of ground and water beds is subject to increasingly strict regulations. A lot of attention is being given to the decontamination of industrial terrains, which can thereafter be used for further redevelopment. In the particular case of water beds, stringent regulations are being introduced relating to the amount of contaminated dredged up species which has to be processed. For instance the Dutch Government has stated that 20% of all contaminated slurry species must be processed in the year 2000.
Known processes for treating slurry include ozone treatment.
Ozone has been shown to react with organic compounds in two ways (Langlais, B. et al., 1991; Ozone in water treatment. Application and Engineering, Chelsea, Mich., USA, Lewis Pulbishers Inc., Nelson, C. H., Brown, R. A., 1994. Adapting ozonation for soil and ground water clean up. In; Chemical Engineering pp. EE 18-25)), by direct reaction by means of electrophylic or cyclo-addition and by indirect reaction via free radicals, formed from ozone after reaction with water or other compounds.
Under direct reaction, ozone reacts firstly with double bonds (C.dbd.C, C.dbd.C--O--R, C.dbd.C--X) or with atoms which are negatively charged (N, P, O, S, and nucleophilic carbon atoms). A high reactivity is therefore envisaged for ortho-activated aromatic compounds by OH, CH.sub.3 or OCH.sub.3. Dependent on the structure of products of the primary oxidation, ozone can also react with this.
Indirect ozone oxidation is non selective. In this instance, oxidation is carried out via a radical mechanism in which differing organic compounds can take part.
Under oxidation of aromatic compounds or polycyclic aromatic compounds (PAH's) the aromatic ring reacts first, resulting in decyclisation and loss of the aromatic structure or side chains. The primary formed products are unsaturated acids and quinones.
The international patent application PCT/DK88/00024 and the Journal of Environmental Science and Health, vol. A17, no. 5, 1982 Baton Rouge (USA) describe processes of ozone treatment.
Problems with these processes, however include controllability, and the cost inefficient consumption of ozone.
It is an object of the present invention to provide a method for the treatment by ozone of contaminated slurry, wherein the process is controllable and wherein ozone consumption is minimized.